Municipalities and other entities such as universities and prisons that meet certain standards must obtain NPDES permit coverage for discharges of stormwater from their municipal separate storm sewer systems (MS4s).
A municipal separate storm sewer is any conveyance or system of conveyances (including but not limited to streets, ditches, and pipes) that is:
- owned by a municipality or other public body (created under state law) having jurisdiction over disposal of sewage, industrial wastes, stormwater or other wastes;
- designed or used for collecting or conveying stormwater;
- not a combined sewer (i.e., not intended for both sewage and stormwater); AND
- not part of a publicly owned treatment works (POTW).
MS4s are categorized as Large, Medium and Small based on criteria in the federal regulations at 40 CFR 122.26. Large and Medium MS4s must apply for NPDES permit coverage. In Pennsylvania there are two Large MS4s, no Medium MS4s, and 953 Small MS4s.
Small MS4s must apply for NPDES permit coverage or a waiver if they are located in an urbanized area as determined by the latest Decennial Census by the U.S. Census Bureau, or if they are designated as needing a permit by DEP. EPA has posted Urbanized Area Maps from the 2010 census data. Urbanized Area information from the 2000 census can also be reviewed at the U.S. Census Bureau 2000 Urbanized Areas Information website.
Waivers may be granted in lieu of permit coverage if the criteria in 40 CFR 122.32(d) or (e) are met.
Small MS4s eligible for general permit coverage are currently covered by the 2013 PAG-13 General Permit (PDF) (3800-PM-BPNPSM0100) until March 15, 2018.
Small MS4s required to obtain permit coverage may, if eligible, apply for coverage under the new 2018 NPDES General Permit for Stormwater Discharges from Small MS4s (PAG-13) (3800-PM-BCW0100) that will be effective starting March 16, 2018. Small MS4s that are ineligible for PAG-13 General Permit coverage may apply for an individual permit (3800-PM-BPNPSM0200).
If the Small MS4 believes that the criteria for a waiver are met, the MS4 may submit an application for a waiver. Waiver applications must be submitted in conjunction with the PAG-13 Notice of Intent (NOI) or the individual permit application, as applicable. An MS4 that would be ineligible for PAG-13 coverage should submit the individual permit application, rather than a PAG-13 NOI, with their waiver application.
Large and Medium MS4s must apply for individual NPDES permits in Pennsylvania, as no NPDES General Permit exists for these MS4s.
Permit coverage is generally for a 5-year term with a requirement to submit a renewal application or NOI at least 180 days prior to the expiration date of coverage. When the statewide PAG-13 General Permit is reissued by DEP, as was done in March 2013, MS4s covered by the previous PAG-13 General Permit are automatically covered by the reissued PAG-13 General Permit if a timely NOI is submitted by the MS4. New requirements may then apply to the MS4. The MS4 can, if it chooses, elect to apply for an individual NPDES permit in lieu of continued coverage under the reissued General Permit.
DEP has developed a reporting tool that can be used to generate lists of NPDES-permitted and waived MS4s in Pennsylvania.
DEP's regional offices inspect MS4s to determine whether the MS4 is meeting its permit obligations. The inspections are documented on DEP's MS4 inspection report (PDF) (3800-FM-BPNPSM0489). DEP also reviews periodic reports (PDF) (3800-FM-BPNPSM0491) submitted by MS4s to DEP.
For more information on MS4 NPDES permits and compliance, email the Bureau of Clean Water (BCW) at RA-EPPAMS4@pa.gov, or contact BCW by phone at 717-787-5017.
DEP published the final NPDES General Permit for Stormwater Discharges from Small MS4s ("PAG-13") in the Pennsylvania Bulletin on June 4, 2016. DEP received over 600 comments on the draft PAG-13 General Permit that was published on May 30, 2015, and has prepared a comment-response document. The final PAG-13 General Permit will become effective on March 16, 2018. The General Permit package includes an NOI form, a waiver application, a model ordinance, instructions for developing Pollutant Reduction Plans, a fact sheet and related materials.
DEP has also published individual NPDES permit application documents for small MS4s on its website for those MS4s that cannot utilize the PAG-13 General Permit, such as MS4s with a requirement to develop a TMDL Plan or discharge to special protection waters. DEP will accept comments or suggestions on these documents through its MS4 email resource account, RA-EPPAMS4@pa.gov.
For clarification purposes, the PAG-13 General Permit that will become effective on March 16, 2018 is, in the paragraphs below, referred to as the "2018 PAG-13 General Permit", and the PAG-13 General Permit that is currently in effect is referred to as the "2013 PAG-13 General Permit".
For the forthcoming permit term, the submission due dates for NOIs and individual permit applications are as follows:
- MS4s with existing coverage under the 2013 PAG-13 General Permit that will be eligible for and desire continued coverage under the 2018 PAG-13 General Permit must submit an NOI by September 16, 2017. If an MS4 determines that it is eligible for a waiver, a waiver application may accompany the NOI.
- MS4s with existing coverage under the 2013 PAG-13 General Permit that will NOT be eligible for continued coverage under the 2018 PAG-13 General Permit must submit an application for an individual NPDES permit by September 16, 2017. These MS4s will have permit coverage under the 2018 PAG-13 General Permit until DEP issues a final individual NPDES permit. If an MS4 determines that is eligible for a waiver, a waiver application may accompany the permit application.
- MS4s with existing individual NPDES permit coverage must submit an individual permit application by September 16, 2017 or at least 180 days prior to the expiration date specified on page 1 of the permit, whichever is later.
- MS4s with existing waivers must submit an NOI (if eligible for PAG-13) or an individual permit application at least 180 days prior to the expiration date of the waiver. If an MS4 determines that it continues to be eligible for a waiver, a waiver application may accompany the NOI or application.
- All MS4s that must apply for permit coverage or a waiver for the first time as a result of the 2010 census must submit their NOI (if eligible for PAG-13) or an individual permit application by September 16, 2017. If an MS4 determines that it is eligible for a waiver, a waiver application may accompany the NOI or application.
For the next permit term, MS4s that discharge to surface waters impaired for certain pollutants or that discharge to waters in the Chesapeake Bay watershed will need to develop TMDL Plans or Pollutant Reduction Plans. To assist MS4s with understanding their obligations regarding impaired waters, DEP has prepared an MS4 Requirements Table. The Table consists of two parts – one for Municipal MS4s (PDF) and one for Non-Municipal MS4s (PDF). See also the Instructions (PDF) for understanding and using the Table and for methods to provide comments. DEP will continue to solicit comments on this table to ensure that all discharges to impaired waters are accurately represented.
An update to the MS4 "Frequently Asked Questions (FAQ) (PDF)" document has been published. It provides good general background information as well as concepts relevant to Pollutant Reduction Plans and TMDL Plans.
DEP has developed a web-based GIS application that provides a visual representation of the information contained in the MS4 Requirements Table.